Conventionally, a touch panel display formed by arranging a touch panel on a liquid crystal display in a lamination manner has been widely used for small equipment such as a mobile phone and a PDA, because a screen and a coordinate input means are collectively provided for saving of a space.
As the above-mentioned touch panel, a resistive film type that is simple in structure, thin in thickness and excellent in mass production has generally used. A configuration thereof is as follows: an upper electrode plate having a flexibility as an operation side and a lower electrode plate as a fixed side are oppositely arranged with a predetermined gap by a spacer, and electric circuits are wired in an X direction and a Y direction on an inner surface of each of the electrode plates.
When a surface of the upper electrode plate is pressed with a stylus pen or the like, the upper electrode plate comes into contact with the lower electrode plate to cause an electric potential gradient to be formed between the electrodes, and by taking out the voltage to the outside to calculate an X-axis position and a Y-axis position with a controller, an input point thus pressed is specified.
FIG. 8 shows an assembly method for the above-mentioned touch panel. An upper electrode plate 50 and a lower electrode plate 51 are oppositely arranged. The upper electrode plate 50 is provided with strip-shaped electrodes 50a, 50b in an X direction, while the lower electrode 51 is provided with strip-shaped electrodes 51a, 51b in a Y direction.
The electrodes 50a, 50b, 51a, 51b are extendedly provided to a connecting part 52 provided on an edge of the touch panel so as to be collectively arranged into one point. The connecting part 52 is connected with conductors 53a of lead wires 53 formed of an FPC (Flexible Printed Circuit Board).
In detail, the conductors 53a are designed to be connected to respective electrodes by a conductive paste, and then fixed and held between the upper electrode plate 50 and the lower electrode plate 51 (for example, refer to FIG. 8 of JP-A 09-50731). Further, in the figure, 50c and 51c denote resistive films formed on inner surfaces of the upper electrode plate 50 and the lower electrode plate 51, respectively.
In such a method for connecting lead wires, lead wires are pulled out directly of a side face of the touch panel. In addition, the upper electrode plate 50 is made of a resin sheet and each electrode is made of a silver paste, so that it cannot be said that the electrode itself is rigid. Furthermore, the conductors 53a of the lead wires 53 are connected to the electrodes with a conductive paste of weak fixing force. Therefore, if a little stronger force acts on the lead wire, the wire can be disconnected at the connecting part 52, so that an extreme care has been required to handle the wire.
On the other hand, there has also been proposed the following method by which a damage to a lead wire connecting part is eliminated and the handling of a wire is easily performed.
For example, in a touch panel shown in FIG. 9, four through holes 51d to 51g are provided by perforation to form connecting parts on an edge of the lower electrode plate 51. Concave-type (female-type) connecting metal fixtures 55 are disposed to be buried in the through holes after a conductive paste 54 has been poured thereinto so as to be electrically connected with the electrodes 50a, 50b, 51a, 51b (for example, refer to FIG. 1 of JP-A 09-50731).
In such a touch panel, a signal from the electrodes 50a, 50b, 51a, 51b can be taken out to the outside while maintaining an electrically good connection without pulling the lead wires out directly of the side face of the touch panel.
However, in such a method for taking out a signal by the use of the connecting metal fixtures 55, there is an inconvenience, in that when a touch panel is mounted on a device such as an interface board or a liquid crystal display, four connecting pins for inserting the connecting metal fixtures 55 into positions corresponding to the through holes 51d to 51g must be erectly provided in the device, thereby requiring a change in lead wire connecting structure for both the touch panel and the above-mentioned device.
The present invention has been made in view of the inconvenience in the conventional method for connecting lead wires to the touch panel, and provides a method for connecting lead wires to a touch panel, enabling a connecting strength of lead wires to be increased without requiring a significant design change.